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Detection of Live Escherichia coli O157:H7 Cells by PMA-qPCR
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Rapid and specific detection, molecular epidemiology, and experimental virulence of the O16 subgroup within

James R Johnson1, Olivier Clermont, Brian Johnston

  • 1Veterans Affairs Medical Center, Minneapolis, Minnesota, USA.

Journal of Clinical Microbiology
|February 7, 2014
PubMed

Insights

A new PCR method identifies the O16-associated Escherichia coli ST131 clade, a multidrug-resistant pathogen distinct from the classic O25b:H4 type. This globally distributed clade shows specific resistance and susceptibility patterns.

Area of Science:

  • Microbiology and Infectious Diseases
  • Genetics and Genomics
  • Epidemiology

Background:

  • Escherichia coli sequence type 131 (ST131) is a major multidrug-resistant extraintestinal pathogen, typically serotype O25b:H4.
  • A distinct O16:H5 clade within ST131 exists, challenging current typing methods.
  • Existing PCR assays and MLST systems may not accurately differentiate these ST131 clades.

Purpose of the Study:

  • To develop a novel PCR-based method for rapid and specific detection of the O16-associated ST131 clade.
  • To characterize the genetic and virulence profiles of the O16 ST131 clade.
  • To assess the global distribution and antimicrobial resistance patterns of the O16 ST131 clade.

Main Methods:

  • Development and validation of a novel PCR assay targeting the O16-associated ST131 clade.
  • Multilocus sequence typing (MLST) using Achtman and Pasteur systems.
  • Analysis of specific gene alleles (fimH, gyrA, parC) and virulence genotypes.
  • Inclusion of a mouse subcutaneous sepsis model for virulence assessment.
  • Epidemiological analysis of clinical E. coli collections.

Main Results:

  • The novel PCR assay successfully and specifically detected the O16-associated ST131 clade.
  • This clade uniformly possessed fimH allele 41 and a narrow range of gyrA and parC alleles.
  • Virulence profiles were similar to classic O25b:H4 ST131 isolates, with variable lethality in mice.
  • The O16 ST131 clade is globally distributed, comprising 1-5% of E. coli isolates.
  • Compared to other ST131, the O16 clade showed resistance to ampicillin, gentamicin, and trimethoprim-sulfamethoxazole, but susceptibility to fluoroquinolones and extended-spectrum cephalosporins.

Conclusions:

  • A novel, specific PCR assay facilitates the identification of the emerging O16-associated ST131 E. coli clade.
  • This clade represents a significant, globally distributed variant of ST131 with distinct antimicrobial resistance characteristics.
  • Further epidemiological and clinical surveillance of this O16 ST131 clade is warranted.

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